In recent years surgery has markedly advanced through the performance of laparoscopic and endoscopic surgical procedures such as cholecystectomies, gastrostomies, appendectomies, and hernia repair. Also, the application of endoscopic surgical stapling and suturing instruments has been provided in cardiovascular and pulmonary surgery, as well as operative inventions in the gastrointestinal tract. Such endoscopic instruments are capable of providing hemostasis and also of cutting tissue. This reduces operating and recuperation time. These stapling procedures are accomplished through a trocar assembly, which is a surgical instrument used to puncture a body cavity. The trocar contains a sharpened obturator tip and a trocar tube or cannula. The trocar cannula is inserted into the skin to access the body cavity, by using the obturator tip to penetrate the skin. After penetration, the obturator is removed and the trocar cannula remains in the body. It is through this cannula that surgical instruments are placed. Specifically, it is through this trocar cannula that surgical stapling instruments with cutting mechanisms are placed. One such trocar is the Endopath.RTM. trocar manufactured by ETHICON ENDO-SURGERY, Cincinnati, Ohio.
Nonetheless, certain deficiencies in current concepts for endosurgical stapling, cutting, clip applying, and grasping mechanisms have been recognized. One perceived deficiency in current surgical articulating instruments is that when loaded, the articulating head on the instrument tends to move. This movement is usually a combination of piece part deflection and slop (or backlash) in the articulation mechanism. High loads on the distal tip of the instrument (e.g., tissue clamping and staple firing) are reflected through the articulation device into the articulation control near the handle and can move (or rotate) the articulation control mechanism. In the past, articulation joints were designed with the articulation device performing double duty as the means for both positioning and locking the articulated head of the instrument.
An examination of the force application points for the load (tip of the instrument) and the articulation device (near the articulation joint) reveals a mechanical disadvantage for the articulating device. This disadvantage manifests itself as a magnification of tolerances or clearances in the articulating device, resulting in significant head movements.
In existing articulating surgical instruments, the rigid shaft of the instrument is sometimes pivotally connected to the surgical head of the instrument with a pivot mount, such as a pin, hinge, or other joint mechanism. While such mechanisms offer the advantage of a precise, tight bend, this same advantage creates a perceived disadvantage, in that increased transmission force may be required in order to drive a surgical tool, such as a knife, around a tight bend, which force is magnified as the angle of articulation increases.
Wedge sled and knife assemblies are generally known in the art. In general, however, such assemblies are not self-contained within the staple cartridge, rely on more expensive metal, as opposed to plastic wedges, present problems of cutting and stapling in an axis which is not colinear with the shaft, present technical difficulty associated with incorporating a spent cartridge lockout in an articulating joint, do not provide a new knife for each firing, and may not completely contain the sharp edge of the knife within the cartridge at the initial and final positions of the linear cutting procedure, creating the potential for injury to the user.
A design criteria in creating a system containing two separate mechanisms for clamping and firing tissue is the limitation of the human hand. Therefore, it is difficult to properly and conveniently position a pair of triggers or a pushbutton mechanism coupled with a trigger mechanism. Thus, there has been little focus or incentive to create stapling mechanisms whereby the user is capable of operating a stapler with two strokes, unless both can be accomplished in a one-handed operation without moving that hand from the handle of the instrument.
Naturally, it would be desirable to be able to perform these functions in a fully rotational system. This simply allows the user to obtain virtually any angle of approach to the surgical site without having to contort the arm of wrist in order to adequately approach the subject.
Furthermore, it would be advantageous to provide the capability to remotely articulate the surgical, e.g., clamping and stapling end of the instrument, such that the angular orientation of the end of the instrument may be adjusted even after the instrument has been inserted through the cannula.
It is also desirable to have distal contact of the stapling jaws, and then proximal clamping. "Distal contact" means that the distal or far end of the anvil seats first on the gap spacing pin or cartridge. Without such distal contact, the surgeon may still be uncertain about the amount of tissue clamped, and therefore the firing force necessary to fire the mechanism. In this way, once distal contact is effectuated, the surgeon realizes and can actually visualize, through an endoscopically placed camera, the amount of tissue clamped between the jaws. Also, distal contact helps prevent tissue from slipping out of the jaws during a clamping sequence.
Additionally, it would be advantageous to provide a knife assembly that included a safety feature, whereby following a cutting sequence, the knife retracts or otherwise is shielded from the operator of the instrument, reducing the likelihood of an inadvertent cutting of the patient or the operator.
Also, it would be highly desireable to provide a device for locking the head of an articulating surgical instrument in an articulated position.
Finally, it would be useful to provide an articulation connection having a flexible neck connecting the rigid shaft of the surgical instrument to a surgical head assembly, providing for a smoothly radiused bend, allowing smoother transmission of force around the bend than is possible with sharper bends achieved through an articulation joint.